Hi all, I live in a flood risk area and the existing suspended floor air vents are at ground level. Anyone know of any ready made external cranked (periscope) air brick extenders to lift the external vent openings by about 800mm? I have made one up, as proof of concept, using 6" rectangular ducting but this is a very expensive way of doing it and the way to firmly fix and seal the bottom of the vent to the house is problematic. These need to be very robust to withstand flood water passing outside the walls. If these are not already available then maybe a business opportunity for somebody?